LA-13638 Approved for public release; distribution is unlimited. A Review of Criticality Accidents 2000 Revision ENERGY POWER TIME Los Alamos NATIONAL LABORATORY Los Alamos, New Mexico 87545 Los Alamos National Laboratory is operated by the University of California for the United States Department of Energy under contract W-7405-ENG-36. Printing coordination by Jerry Halladay and Guadalupe Archuleta, Group CIC-9 Photocomposition by Wendy Burditt, Group CIC-1 Cover Design by Kelly Parker, Group CIC-1 Cover Illustration: Power and energy traces representative of a typical criticality excursion in solution - from the SILENE experimental report, reference # 4. An Affirmative Action/Equal Opportunity Employer This report was prepared as an account of work sponsored by an agency of the United States Government. Neither The Regents of the University of California, the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by The Regents of the University of California, the United States Government, or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of The Regents of the University of California, the United States Government, or any agency thereof.Los Alamos National Laboratory strongly supports academic freedom and a researcherÕs right to publish; as an institution, however, the Laboratory oesd not endorse the viewpoint of a publication or guarantee its technical correctness. A Review of Criticality Accidents 2000 Revision LA-13638 Issued: May 2000 United States Authors: Thomas P. McLaughlin Shean P. Monahan Norman L. Pruvost* Russian Federation Authors: Vladimir V. Frolov** Boris G. Ryazanov*** Victor I. Sviridov† *Senior Analyst. Galaxy Computer Services, Inc., Santa Fe, NM 87501. **Lead Researcher. Institute of Physics and Power Engineering (IPPE), Obninsk, Russia 249020. ***Head of the Nuclear Safety Division. Institute of Physics and Power Engineering (IPPE), Obninsk, Russia 249020. †Head of the Nuclear Safety Laboratory. Institute of Physics and Power Engineering (IPPE), Obninsk, Russia 249020. Los Alamos NATIONAL LABORATORY Los Alamos, New Mexico 87545 FOREWARD We, of the early decades at Pajarito Site, Los Alamos, were near a number of accidental bursts of radiation in the course of critical experiments. In the first of these, the person at the controls exclaimed “a disaster!” With a quarter-mile separation protecting operators, each of these “disasters” proved to be without consequence. Nevertheless, errors that led to them should have been avoided, and accounts of these accidents were disseminated to discourage recurrence. A serious process criticality accident at Los Alamos was another matter, because protection of operators was supposed to have been provided by criticality safety practices instead of built-in features such as shielding or distance. In this case, publication brought out obscure causes that demanded consideration in the discipline of criticality safety. The value of publication of both types of accident led William R. Stratton of the Pajarito Group to bring together all available descriptions in his A Review of Criticality Accidents, the linchpin of this account. Hugh C. Paxton Los Alamos, NM August 1999 v PREFACE This document is the second revision of A Review of Criticality Accidents. The first was issued as report LA-3611 in 1967 and authored by William R. Stratton.1 At that time, he was a staff member in the Critical Experiments Group at Los Alamos and a member of the Atomic Energy Commission’s Advisory Committee on Reactor Safeguards. The first revision was pub- lished with the same title in 1989 as document NCT-04.2 This revision was carried out by David R. Smith, a colleague of Stratton’s in the Critical Experiments Group during the 60’s and 70’s and the Laboratory’s Criticality Safety Officer. In 1980, the criticality safety function was removed from the Critical Experiments Group and made a separate entity in the Laboratory’s Health and Safety organization with Smith as the first group leader. With the advent of cooperative research and information exchanges between scientists in the Russian Federation (Russia, R.F.) of the Former Soviet Union and Los Alamos National Labora- tory in the early 1990s, discussions began to investigate possible joint work in the field of nuclear criticality safety (to be referred to hereafter as simply “criticality safety”). By 1994, interactions were ongoing between Los Alamos and four Russian sites with criticality safety interests: the Institute of Physics and Power Engineering (IPPE) in Obninsk; the All Russian Scientific Re- search Institute of Experimental Physics (VNIIEF) in Sarov (formerly Arzamas-16); the All Russian Scientific Research Institute of Technical Physics (VNIITF) in Snezhinsk (formerly Chelyabinsk-70); and the Kurchatov Institute (KI) in Moscow. Criticality safety staff at IPPE have regulatory oversight responsibility for the four major fissile material production and handling sites where process facility criticality accidents have occurred. These are the Mayak Production Association (Mayak), the Siberian Chemical Combine (Tomsk-7) in Seversk, the Electrostal Machine Building Plant in Electrostal, and the Novosibirsk Chemical Concentrates Plant in Novosibirsk. Thus, criticality safety staff from these four sites were directly involved in the 13 Russian process accidents described herein. The other three institutes, Arzamas-16, Chelyabinsk-70, and the Kurchatov Institute have critical experiment and reactor development capabilities; accidents in this category have occurred at these sites. This report, planned to be published in both English and Russian language versions, is the fruit of cooperative efforts of criticality safety specialists in both countries. It not only includes all of the Russian criticality accidents, but also revises the US and UK process facility accidents reported in the second edition. The revisions to the US and UK process accident descriptions are mainly expansions of the text to include information that was previously only in reference docu- ments. In a few instances, technical corrections were necessary. The expanded descriptions are provided for the benefit of the broader audience that this document has been attracting over the years. Finally, as this report was almost to be printed in September 1999, a criticality accident occurred at the JCO fuel processing facility in Japan. Printing was delayed until this most recent accident could be fully understood and documented herein. It is the goal of the authors that with this expanded report, the causes of criticality accidents and their consequences will be better understood and the safety and efficiency of operations with significant quantities of fissile mate- rials will be enhanced. vii ACKNOWLEDGMENTS Many people have contributed significantly to the completion of this second revision of A Review of Criticality Accidents. The relative importance of the contribution of each person is not intended by the ordering of names. Each person made a necessary contribution to the final document. For the Russian accident information: Gennadiy T. Kirillov—Tomsk-7 Mikhail I. Kuvshinov—Arzamas-16 Dimitri M. Parfanovich—Kurchatov Institute Aleksandr V. Romanov—Electrostal Igor G. Smirnov—Arzamas-16 Gennadiy S. Starodubtsev—Mayak A. P. Suslov—Mayak Vladimir Teryokhin—Chelyabinsk-70 Aleksandr G. Ustyugov—Novosibirsk Sergei Vorontsov—Arzamas-16 Isao Takeshita—Japanese Atomic Energy Research Institute The U.S. authors are indebted to each of the above for answering innumerable questions, often by telephone, at home, late at night in Russia in order to accommodate a mid-morning meeting time in Los Alamos. In particular, we acknowledge that Igor G. Smirnov, Sergei Vorontsov, Mikhail I. Kuvshinov, and Vladimir Teryokhin endured about three hours of “interro- gation” one night at one of the Los Alamos authors’ homes, and were recompensed only with a meal. On another occasion, after a similar evening of questions and discussion, Gennadiy Starodubtsev agreed to return two evenings later for another four-hour session, each time accept- ing only a meal as payment. These evening sessions took place after a full day of other business in Los Alamos. Gennadiy Starodubtsev was motivated by a personal desire to contribute to an accurate, complete recounting of the seven Mayak accidents. Barbara D. Henderson played a key administrative role in keeping the project on track in many regards. She has been involved with the project from the time it was only an ill-defined goal to the final product, a nearly eight-year span. Charles T. Rombough assisted with this project for more than two years. He has provided seamless transmission of information, text, figures, and photographs, in both English and Rus- sian languages, in addition to producing electronic files of all intermediate drafts. Nellie Schachowskoj Shropshire and Olga Viddo provided both interpretation and translation services for the many meetings, telephone calls, emails, and intermediate